Neutron and X-ray diffraction study of the broken symmetry phase transition in solid deuterium

The solid hydrogen compounds D2, HD and H2 remain quantum molecular solids up to pressures in the 100 GPa range. A remarkable macroscopic consequence is the existence of a pressure-induced broken symmetry phase transition, in which the molecules go from a spherical rotational state to an anisotropic rotational state. Theoretical understanding of the broken symmetry phase structure remains controversial, despite numerous studies. Some open questions concern the existence of long- or short-range orientational order; whether a strong isotopic shift on the transition pressure should be assigned to the nuclear zero-point motion or to quantum localization; and whether the structures are cubic, hexagonal or orthorhombic. Here we present experimental data on the structure of the broken symmetry phase in solid D2, obtained by a combination of neutron and X-ray diffraction up to 60 GPa. Our data are incompatible with orthorhombic structures predicted by recent theoretical works. We find that the broken symmetry phase structure is incommensurate with local orientational order, being similar to that found in metastable cubic para-D2.     

TLR signalling augments macrophage bactericidal activity through mitochondrial ROS

Reactive oxygen species (ROS) are essential components of the innate immune response against intracellular bacteria and it is thought that professional phagocytes generate ROS primarily via the phagosomal NADPH oxidase machinery. However, recent studies have suggested that mitochondrial ROS (mROS) also contribute to mouse macrophage bactericidal activity, although the mechanisms linking innate immune signalling to mitochondria for mROS generation remain unclear. Here we demonstrate that engagement of a subset of Toll-like receptors (TLR1, TLR2 and TLR4) results in the recruitment of mitochondria to macrophage phagosomes and augments mROS production. This response involves translocation of a TLR signalling adaptor, tumour necrosis factor receptor-associated factor 6 (TRAF6), to mitochondria, where it engages the protein ECSIT (evolutionarily conserved signalling intermediate in Toll pathways), which is implicated in mitochondrial respiratory chain assembly. Interaction with TRAF6 leads to ECSIT ubiquitination and enrichment at the mitochondrial periphery, resulting in increased mitochondrial and cellular ROS generation. ECSIT- and TRAF6-depleted macrophages have decreased levels of TLR-induced ROS and are significantly impaired in their ability to kill intracellular bacteria. Additionally, reducing macrophage mROS levels by expressing catalase in mitochondria results in defective bacterial killing, confirming the role of mROS in bactericidal activity. These results reveal a novel pathway linking innate immune signalling to mitochondria, implicate mROS as an important component of antibacterial responses and further establish mitochondria as hubs for innate immune signalling.     

The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans

Choanoflagellates are the closest known relatives of metazoans. To discover potential molecular mechanisms underlying the evolution of metazoan multicellularity, we sequenced and analysed the genome of the unicellular choanoflagellate Monosiga brevicollis. The genome contains approximately 9,200 intron-rich genes, including a number that encode cell adhesion and signalling protein domains that are otherwise restricted to metazoans. Here we show that the physical linkages among protein domains often differ between M. brevicollis and metazoans, suggesting that abundant domain shuffling followed the separation of the choanoflagellate and metazoan lineages. The completion of the M. brevicollis genome allows us to reconstruct with increasing resolution the genomic changes that accompanied the origin of metazoans.     

Patterns of relative species abundance in rainforests and coral reefs

A formidable many-body problem in ecology is to understand the complex of factors controlling patterns of relative species abundance (RSA) in communities of interacting species. Unlike many problems in physics, the nature of the interactions in ecological communities is not completely known. Although most contemporary theories in ecology start with the basic premise that species interact, here we show that a theory in which all interspecific interactions are turned off leads to analytical results that are in agreement with RSA data from tropical forests and coral reefs. The assumption of non-interacting species leads to a sampling theory for the RSA that yields a simple approximation at large scales to the exact theory. Our results show that one can make significant theoretical progress in ecology by assuming that the effective interactions among species are weak in the stationary states in species-rich communities such as tropical forests and coral reefs.     

Fuzzy linear model for production optimization of mining systems with multiple entities

Planning and production optimization within multiple mines or several work sites (entities) mining systems by using fuzzy linear programming (LP) was studied. LP is the most commonly used operations research methods in mining engineering. After the introductory review of properties and limitations of applying LP, short reviews of the general settings of deterministic and fuzzy LP models are presented. With the purpose of comparative analysis, the application of both LP models is presented using the example of the Bauxite Basin Niksic with five mines. After the assessment, LP is an efficient mathematical modeling tool in production planning and solving many other single-criteria optimization problems of mining engineering. After the comparison of advantages and deficiencies of both deterministic and fuzzy LP models, the conclusion presents benefits of the fuzzy LP model but is also stating that seeking the optimal plan of production means to accomplish the overall analysis that will encompass the LP model approaches.     

Investigation of coupled cobalt–silver nanoparticle system by plan view TEM

We present a transmission electron microscopy (TEM) investigation of a coupled cobalt and silver nanoparticle system. A plan view in situ lift-out method for preparing samples for TEM using the focused ion beam (FIB) microscope was used. This technique is used to prepare high quality TEM samples with site specificity in a short time and with a high success rate. We demonstrate the ability of the plan view sample preparation technique to provide information about an ordered system of nanoparticles which could not be observed using standard FIB cross sectioning of the sample. High resolution TEM and energy dispersive X-ray spectroscopy mapping of both cross sectional and plan view samples are presented, clearly showing the significant benefit of plan view TEM analysis for certain samples